Transit officials are waiting on test results to determine whether they must delay construction on the Silver Line extension to Dulles International Airport.

Charles Stark, the director of the Dulles Corridor Metrorail project, said the concrete used to build wall panels at stations on the Silver Line extension may be subject to a swelling chemical reaction that causes cracks and critical structural problems, WTOP reported Friday.

To gauge the extent of the reaction, a laboratory will test concrete samples and release results in seven to eight weeks. The results will determine whether the problem can be solved by applying sealant or if the panels need to be replaced entirely, WTOP reported.

Stark said the reaction only affects the durability of the concrete wall panels, not their strength.

“With regard to safety, the strength of the concrete has never been in question,” he told WTOP.

Metropolitan Washington Airports Authority CEO Jack Potter said replacing the panels – which would delay the project set to open to riders in 2020 – is “on the table, if required.”

“We’re going to let the science drive our decisions,” he told WTOP.

Loudoun County Board of Supervisors Chair Phyllis Randall added that a delay would tack on more expenses to the more than $1 billion project.

“Obviously, it is more important to get it right than to do it quickly,” she said.

The issue is the most recent problem the project has faced regarding the integrity of concrete used on site. Nathan Davidheiser – an employee at Universal Concrete Products, the concrete panel manufacturer – filed a whistleblower lawsuit in March 2016 alleging that the company produced faulty panels and directed him to lie about quality control tests, according to the WTOP report.

Officials at Capital Rail Constructors, the contractor responsible for construction, also said earlier this month that the concrete panels had too much water mixed into them, a possible accelerant to the deterioration process. The contractor agreed to put sealant on the panels to keep water out and to repeat the process every decade, according to WTOP.

“I am concerned that there could be a delay,” Fairfax County Board of Supervisors Chairman Sharon Bulova said. “On the other hand, if a delay is required in order to ensure safety, that’s what needs to happen.”